I am in the market for a collapsible stock for my SP-1 project, got my new Colt 16" pre ban lightweight barrel, Thanks J&T! Have a new correct flat delta ring assem, have a like new SP-1 Colt large hole non-forward assist upper, will be ordering my bolt and carrier assem from Bushmaster. What type of stock would be correct for this 1981 period SP-1 carbine? I know the original ones had a 2 position stock, should I get a aluminum or fiberite plastic? All of the companies that advertise new Colt stocks are out of stock! Would the one that Bushmaster sells be close to correct? Aluminum or Plastic?
Thanks in advance!

yes, they should all be mil-spec in theory and be interchangeable.    try cheaperthandirt.com and cdnninventments.com

I have a factory original SP1 carbine from that era. It has a 2 position aluminum collapsible stock. The buffer tube is aluminum, the stock is semi-gloss black.

It's similar to what Bushmaster calls an "Original Style Fiberite TeleStock". It's different from the current 6 position Fiberite TeleStock.

I have a similar stock from a later Colt rifle I might sell for the right price. E-mail me if you're interested.